Primes that remain prime through 4 iterations of function f(x) = 10x + 9.

Terms

a(0) =13a(1) =139a(2) =293a(3) =1889a(4) =2939a(5) =3719a(6) =6089a(7) =7741a(8) =12823a(9) =19753a(10) =21391a(11) =22861a(12) =28513a(13) =36721a(14) =37967a(15) =40949a(16) =60899a(17) =76519a(18) =83621a(19) =101747a(20) =121687a(21) =127549a(22) =128239a(23) =142099a(24) =149197a(25) =153817a(26) =155581a(27) =158489a(28) =160159a(29) =169283